2. Membrane potentials Flashcards
An electrical potential (potential difference) that exists across the plasma membrane
membrane potential
Charged solutes in body in the ECF are mostly ions, what are they?
Sodium (Na+) = major cation, chloride(Cl-) and bicarbonate(HCO3-) = major anions
charged solutes in the ICF are mostly ions and charged molecules, what are they?
proteins, amino acids, and nucleotides = anions potassium (K+) and magnesium (Mg+) = cations
Body fluids are electrically _____
neutral
what is the principle of macroscopic electroneutrality?
Body fluids are electrically neutral
Are body fluids 100% electrically neutral?
No, ICF has small amount of excess negative charge and ECF has small amount of excess positive charge.
Charge difference across the plasma membrane is called what?
membrane potential
what units is membrane potential measured in?
millivolts (mV)
Size of the potential difference is indicated by the _______ of the membrane potential
magnitude
A negative membrane potential indicates that the ______has excess _______charge and the ______has excess ________charge
ICF; negative; ECF; positive
A positive membrane potential indicates that the _____has excess ________ charge and the ____has excess ________charge
ICF; positive; ECF; negative
Membrane potentials are important for body function. They help drive movement of ______across the plasma membrane, which is important for processes such as _____ ________and _______ ___________, ________ absorption, and _______ _________ ___________.
solutes; plasma filtration; urine production; nutrient; action potential production
When membrane potentials are produced, net ion movement is first determined by several driving forces, what are they called? and what other name do they have?
chemical driving force (chemical potential), electrical driving force (electrical potential), together they are called the electrochemical driving force (electrochemical potential gradient)
Movement of ions down their __________ ________will change the membrane potential
electrochemical gradient
the membrane potential at which an ion’s chemical driving force and the electrical driving force are equal to one another and in opposite directions
equilibrium potential
What net ion movement is found at the equilibrium potential?
none
ions will move in direction that
brings them closer to the equilibrium potential
Do ions contribute to membrane potential?
yes, they all do
Which ions contribute the most to membrane potential?
cl- K+ Na+
The greater permeability of K+ causes the ICF to be slightly what compared to the ECF? Why is that?
negative, bc K+ have a greater tendency to diffuse from ICF to ECF
What structure helps maintain the membrane potential by moving potassium ions and sodium ions up their concentration gradients?
sodium-potassium ATPase pumps
sodium-potassium ATPase pumps also contribute to the ICF being slightly negative, why is that?
the pumps move fewer K+ than Na+
